Need a better understanding of SDI

[Blase Theodore]

(digibeta PAL if it matters)

[Bob Zelin]

Digi Beta is a 4:2:2 signal (it has compression on it) – even in old linear rooms, it was not a RGB 4:4:4 path.

Working with DVCPro50 will use the DVCPro compression codec (which looks very good), but it is not uncompressed video. Up until recently, much of the world considered Digi Beta uncompressed video (except for the purists who would only use the old Sony D1 or Panasonic D5 VTR’s) – but now the HD world purists want Sony SR series dual link 4:4:4 only.

It’s all a bunch of hooey – Digi Beta 4:2:2 8 bit uncompressed looks fantastic – and gets rejected by no TV broadcaster anywhere. It’s been this way before the AVID was even an accepted product (and Blackmagic and AJA were just a dream).

To re-answer your question, a Digi Beta VTR supplies an “uncompressed” 4:2:2 signal coming out of it’s SDI BNC connector – if you consider 4:2:2 to be uncompressed (which most people do).

Bob Zelin

[Matt Silverman]

To clarify, Digibeta is 10bit 4:2:2 with adaptive compression. Some images get slightly compressed, while others are losslessly compressed. I have done some tests which are lossless after multiple generations and others which incur loss.

also, there is no “digibeta” codec. You should use the BM 10bit codec.

Regarding D1 or D5… D1 is uncompressed but 8bit only (and a dead format), which is why it is equivelant to digibeta… it’s a tradeoff of 10bit for slight compression. D5 standard def is uncompressed 10bit (HD is compressed 10bit).

SDI is just a transport stream… it is like a firewire or scsi connector. It just sends the 1’s and 0’s from the tape to your computer without losing any info. The compression and color space compression happen on the tape.

-Matt

[Blase Theodore]

Thanks Bob and Matt.